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  • ItemOpen Access
    High voltage outdoor insulator surface condition evaluation using aerial insulator images
    (IET, 2019-09) Pernebayeva, Damira; Irmanova, Aidana; Sadykova, Diana; Bagheri, Mehdi; James, Alex
    High voltage insulator detection and monitoring via drone-based aerial images is a cost-effective alternative in extreme winter conditions and complex terrains. The authors examine different surface conditions of the outdoor electrical insulator that generally occur under winter condition using image processing techniques and state-of-the-art classification methods. Two different types of classification approaches are compared: one method is based on neural networks (e.g. CNN, InceptionV3, MobileNet, VGG16, and ResNet50) and the other method is based on traditional machine learning classifiers (e.g. Bayes Net, Decision Tree, Lazy, Rules, and Meta classifiers). They are evaluated to discriminate the images of insulator surface exposed to freezing, wet, and snowing conditions. The results indicate that traditional machine learning methods with proper selection of features can show high classification accuracy. The classification of the insulator surfaces will assist in determining the insulator conditions, and take preventive measures for its protection.
  • ItemOpen Access
    Computational Analysis of Transport Across Flake-Filled Composites of Realistic Microstructure
    (Nazarbayev University School of Engineering and Digital Sciences, 2019-02-06) Tsiantis, Andreas; Sumbekova, Sholpan; Papathanasiou, Thanasis D.
    In this paper we present the results of a computational study of diffusion across disordered flake composites in which the flakes are misaligned with respect to the direction of bulk diffusion. We evaluate the effect of flake orientation as well as the influence of boundary conditions and unit-cell types on the predicted barrier properties. Flake orientation impacts very significantly on the barrier properties in flake-filled composites, and usually the key objective in their fabrication is to orient them as close as possible to being perpendicular to the direction of macroscopic diffusion. Our computations are carried out in two-dimensional, doubly-periodic unit cells, each containing up to 3000 individual flake cross-sections. We consider high aspect ratio (alpha) systems with alpha=1000, from the dilute (alpha phi=0.01) and into the very concentrated (alpha phi=40) regime. The effective diffusivity of the corresponding unit cells is computed from the imposed concentration difference and the computed mass flux, using Fick's Law. We show that use of cyclic boundary conditions and doubly-periodic unit cells results in effective diffusivities which are in agreement with theory and invariant of the shape of the unit cell. We also show that the use of adiabatic boundary conditions produces erroneous results at high flake concentrations. Finally we compare our results to the predictions of existing literature models and find that the latter deviate significantly from computation at high flake concentrations.
  • ItemOpen Access
    Efficient Data Aggregation in Wireless Sensor Networks with Multiple Sinks
    (Nazarbayev University School of Engineering and Digital Sciences, 2018-05-12) Saginbekov, Sain; Yestemirova, Gaukhar
    A Wireless Sensor Network (WSN) is a network comprised of sensor nodes and a designated device called a sink to which nodes transmit their sensed data. Nodes are low-cost, battery-powered devices with limited memory and computational power. Usually WSNs are deployed with a single sink and left unattended for a long time. During this time sensor nodes, communication links between the nodes, and the sink may go down or crash due to energy depletion, harsh environment, or for some other reasons. If the sink crashes, then the network becomes useless as the sink will not be able to collect data from nodes. One way of making the network more reliable is to deploy networks with more than one sink. Existing efficient data aggregation protocols developed for WSNs with a single sink may not show the similar efficiency in WSNs with multiple sinks. In this paper, we first define the data aggregation problem in WSNs with multiple sinks, and then propose two data aggregation algorithms for a WSN with multiple sinks that minimize the number of data packet transmissions during data collection. The first one is based on a Minimum Spanning Tree algorithm and the second one is based on a Shortest Path Tree algorithm. Simulation results show the effectiveness of the proposed algorithms.
  • ItemOpen Access
    Detection of the vegetation change cover using landsat TM5 in the Burabay State National Natural Park, Kazakhstan
    (International Scientific and Practical Conference "Geosystemic approach to the study of the natural environment of the Republic of Kazakhstan", 2018-04-13) Taibassarova, Zh.
    The SNNP «Burabay» is the famous touristic place in Kazakhstan, where the frequent climate change and anthropogenic activities has a significant impact in land cover change. Especially, there is significant impact on vegetation lost and these changes have a detrimental impact on biodiversity, as SNPP is defined as a home for 305 animal species and 800 flora species (https: // kazakhstan.orexca.com/ national park burabay.shtml). The tourism industry has become the dominant contributor to Burabay»s development, so many vegetated areas, green spaces are reducing in order to build hotels, restaurants and different types of entertainment centres. Thus, the SNNP « Burabay» is under the control of the International Union for Conservation of Nature (1UCN) in the category 2 which aims: «to protect biodiversity along with its underlying ecological structure and supporting environmental processes, and to promote education and recreation)) (1UCN, 2017 https://www.iucn.org/).
  • ItemOpen Access
    Modeling hydrological ecosystem services and trade-offs under land use land cover change scenarios in the Syrdarya river basin
    (International Scientific and Practical Conference "Geosystemic approach to the study of the natural environment of the Republic of Kazakhstan", 2018-04-13) Meldebekova, G.
    The Syrdarya river basin in Central Asia is facing a strong degradation of ecosystems and water quality deterioration mainly attributed to intensive agriculture. Predicted population growth and land use change call for more comprehensive, integrated management that considers entire coupled social-ecological systems. Within SES (Social-Ecological Systems) framework, the master's thesis is focused on upstream land use change impacts on downstream ecosystem services to reveal the trade-offs. The study performs a biophysical assessment of changes in three hydrological ecosystem services, one provisioning (water supply) and two regulating (water purification and erosion control) by developing spatially explicit models of land use change using Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) software. This assessment was achieved by designing alternative land use scenarios and then exploring the spatial patterns of ecosystem services in order to better understand linkages and consequences of land use change. This research presents an analytical framework for integrating direct human benefits and ecosystem services in policy decision-making and illustrates its application.
  • ItemOpen Access
    BIM-GIS technologies in analysing the cost of assets after natural disasters: water flood and earthquake
    (International Scientific and Practical Conference "Geosystemic approach to the study of the natural environment of the Republic of Kazakhstan", 2018-04-13) Abuov, Y.; Omirtay, O.
    BIM-GIS integration. Analysing the cost of damage of buildings after natural disaster happened is a quite complex process. Methods having now to solve this problem take too many approximations; these models neglect unique parameters of each building. Final cost of damage depends on big number of variables. For example, in case of water flood, those variables can be: 3D geometric parameters of building, unit cost of materials, water velocity, depth of flood, physical properties of material, terrain geometry, etc. There is no single software to run mentioned complex model. This paper suggests integration of Geographic information system (GIS) and Building Information Modeling (BIM) as a method to perform cost analysis after natural disasters happened in given urban place. Both BIM and GIS are software which represent real world in digital format. But BIM uses micro level of objects and handles mainly indoor data while GIS uses macro level which includes rivers, basins and data in outdoor.
  • ItemOpen Access
    Comparison of the hydrological and meteorological project implementations in the different countries
    (Nazarbayev University School of Engineering and Digital Sciences, 2018-04-13) Sagintayev, Zhanay
    Climatic and anthropogenic distortions have impacted the enviroment and increased the probabilities of disaster events worldwide, including Kazakhstan. Water resources in Central Asia are generated at high mountains with snow and glacier melt dominating the flow regime. Increasing temperatures at higher elevations will have an impact on the snow and glacier melting process and this will change the flow regime of Kazakhstan, Central Asian Rivers. A combination of different modeling techniques, including regional climate monitoring, hydrological, hydro-geological, river hydraulics, geothechnical, debris flows, landslides, Artificial Neural Networks (ANN) modeling tools are helpful for prediction analysis and disaster event preparation activities. Some of these modeling techniques are reviewed in this article.
  • ItemOpen Access
    Multi-Objective Optimization Techniques using ANSYS-CFX-DesignXplorerTM. Case Study: Optimization of Static Mixer
    (Nazarbayev University School of Engineering and Digital Sciences, 2017-07) Rojas-Solórzano, Luis R.
  • ItemOpen Access
    Clean EnergyTechnologies:How to assess their viability?
    (Nazarbayev University School of Engineering and Digital Sciences, 2017-07-13) Rojas-Solórzano, Luis R.
  • ItemOpen Access
    Antenna Beamforming for Energy Harvesting in Cognitive Radio Networks
    (2016) Liu, Huidong; Chen, Jin; Ding, Guoru; Tsiftsis, Theodoros A.; Rowell, Corbett
    In this paper, a cooperative cognitive radio network (CRN) with energy harvesting capabilities of its secondary users is considered. Specifically, cooperative spectrum sensing and multi-antenna beamforming are employed to improve the sensing performance and the energy transfer efficiency, respectively. In our approach, a homogeneous CRN scenario is studied where the optimal sensing probability of each second user (SU) is obtained to maximize the control center (CC) throughput while satisfying the energy causality and primary user (PU) collision constraints. An iterative algorithm is proposed to obtain the optimal charging time. Numerical results depict that in an energy constrained scenario, cooperative spectrum sensing with beamforming performs much better than cooperative spectrum sensing without beamforming in terms of increased system throughput
  • ItemOpen Access
    Energy Detection Based Spectrum Sensing over Enriched Multipath Fading Channels
    (2016) Bagheri, Alireza; Sofotasios, Paschalis C.; Tsiftsis, Theodoros A.; Ho-Van, Khuong; Loupis, Michael I.; Freear, Steven; Valkama, Mikko
    Energy detection has been for long constituting the most popular sensing method in RADAR and cognitive radio systems. The present paper investigates the sensing behaviour of an energy detector over Hoyt fading channels, which have been extensively shown to provide rather accurate characterization of enriched multipath fading conditions. To this end, a simple series representation and an exact closed-form expression are firstly derived for the corresponding average probability of detection for the conventional single-channel communication scenario. These expressions are subsequently employed in deriving novel analytic results for the case of both collaborative detection and squarelaw selection diversity reception. The derived expressions have a relatively tractable algebraic representation which renders them convenient to handle both analytically and numerically. As a result, they can be utilized in quantifying the effect of fading in energy detection based spectrum sensing and in the determination of the trade-offs between sensing performance and energy efficiency in cognitive radio communications. Based on this, it is shown that the performance of the energy detector depends highly on the severity of fading as even slight variations of the fading conditions affect the value of the average probability of detection. It is also clearly shown that the detection performance improves substantially as the number of branches or collaborating users increase. This improvement is substantial in both moderate and severe fading conditions and can practically provide full compensation for the latter cases
  • ItemOpen Access
    Resource Allocation for Licensed/Unlicensed Carrier Aggregation MIMO Systems
    (2016) Tsinos, Christos G.; Foukalas, Fotis; Tsiftsis, Theodoros A.
    In this paper a novel Carrier Aggregation (CA) scheme is proposed for downlink MIMO LTE-A Systems. The proposed approach achieves increased transmission rates by establishing the communication links via both licensed and unlicensed bands without generating or experiencing interference to/from the users of the latter bands. To that end, a rate optimization problem is defined and solved subject to the previous zero interference constraints, a total power constraint and a maximum number of aggregated bands constraint. It turns out that the previous problem is a Mixed Integer Non Linear Programming (MINLP) one that requires an exhaustive search procedure in order to be solved. To tackle this, an optimal low complexity method is proposed based on the Lagrange dual decomposition. The performance of the original (MINLP) and the low-complexity proposed techniques is verified via indicative simulations
  • ItemOpen Access
    Energy Efficient Switching between Data Transmission and Energy Harvesting for Cooperative Cognitive Relaying Systems
    (2016) Miridakis, Nikolaos I.; Tsiftsis, Theodoros A.; Alexandropoulos, George C.; Debbah, M´erouane
    A dual-hop cognitive (secondary) relaying system incorporating collaborative spectrum sensing to opportunistically switch between data transmission and energy harvesting is introduced. The secondary relays, first scan the wireless channel for a primary network activity, and then convey their reports to a secondary base station (SBS). Afterwards, the SBS, based on these reports and its own estimation, decides cooperatively the presence of primary transmission or not. In the former scenario, all secondary relays start to harvest energy from the transmission of one or more primary nodes. In the latter scenario, the system initiates secondary communication via a best relay selection policy. The performance of the proposed scheme is thoroughly investigated by assuming realistic channel conditions, i.e., non-identical link-distances and outdated channel estimation, while its overall energy consumption is evaluated, indicating the efficiency of the switching approach.
  • ItemOpen Access
    On the Energy Efficiency in Multi-user Multi-relay Coded Network
    (2016) Qi, Nan; Xiao, Ming; Tsiftsis, Theodoros A.; Cao, Phuong L.; Skoglund, Mikael; Li, Lixin
    In this paper, the energy efficiency (EE) of a cooperative diversity system with maximum diversity network coding (MDNC) is studied. In the considered system, channel state information (CSI) is only available at the receivers for all the channels. We formulate the problem of maximizing the EE under the constraint on the outage probability. The problem is NP-hard due to the non-convexity of the outage probability function and the nonlinear fractional structure of the introduced EE. To solve the optimization problem efficiently, first, the outage probability function is tightly approximated as a log-convex form in the high signal-to-noise ratio (SNR) region. Further, based on the fractional programming, we transform the introduced EE into a subtractive-form, which is proved to be a convex form. The tradeoff between outage probability and EE is given. The results show that our power allocation (PA) policy can substantially increase the EE. We show that EE can be increased if more relays forward the messages. Additionally, we also investigate the effect of the relay locations on the EE and demonstrate that the increase in the transmission distance in the first hop causes the loss of the EE. The loss can be reduced by our PA policy
  • ItemOpen Access
    Simultaneous Spectrum Sensing and Data Transmission for Multi-User MIMO Cognitive Radio Systems
    (2016) Miridakis, Nikolaos I.; Tsiftsis, Theodoros A.; Alexandropoulos, George C.; Debbah, M´erouane
    We present a multi-user multiple-input multipleoutput (MIMO) cognitive radio system consisting of a secondary receiver that deploys spatial multiplexing to decode signals from multiple secondary transmitters, under the presence of primary transmissions. The secondary receiver carries out minimum mean-squared error detection to decode the secondary data streams, while it performs spectrum sensing at the remaining signal to capture the potential presence of primary activity. Assuming Rayleigh fading as well as the realistic cases of channel fading time variation and channel estimation errors, we present novel closed-form expressions for important system measures, namely, the detection and false-alarm probabilities as well as the transmission power of the secondary nodes. The enclosed numerical results verify the accuracy of the presented analysis.
  • ItemOpen Access
    Red Sea Rifting Controls on Groundwater Reservoir Distribution: Constraints from Geophysical, Isotopic, and Remote Sensing Data
    (2008-10) Sturchio, Neil C.; Sagin, Jay; Becker, Richard H.; Ahmed, Mohamed
    Highly productive wells in the Central Eastern Desert of Egypt are tapping groundwater in subsided blocks of Jurassic to Cretaceous sandstone (Taref Formation of the Nubian Sandstone Group) and Oligocene to Miocene sandstone (Nakheil Formation), now occurring beneath the Red Sea coastal plain and within the proximal basement complex. Aquifer development is related to Red Sea rifting: (1) rifting was accommodated by vertical extensional displacement on preexisting NW-SE– to N-S–trending faults forming a complex array of half-grabens and asymmetric horsts; and (2) subsided blocks escaped erosion accompanying the Red Sea–related uplift. Subsided blocks were identifi ed and verifi ed using satellite data, geologic maps, and fi eld and geophysical investigations. Interpretations of very low frequency (VLF) measurements suggest the faults acted as conduits for ascending groundwater from the subsided aquifers. Stable isotopic compositions (δD: –19.3‰ to –53.9‰; δ18O: –2.7‰ to –7.1‰) of groundwater samples from these aquifers are interpreted as mixtures of fossil (up to 70%) and modern (up to 65%) precipitation. Groundwater volumes in subsided blocks are large; within the Central Eastern Desert basement complex alone, they are estimated at 3 × 109 m3 and 10 × 109 m3 for the Nakheil and Taref Formations, respectively. Results highlight the potential for identifying similar rift-related aquifer systems along the Red Sea–Gulf of Suez system, and in rift systems elsewhere. An understanding of the distribution of Red Sea rift–related aquifers and modern recharge contributions to these aquifers could assist in addressing the rising demands for fresh water supplies and water scarcity issues in the region
  • ItemOpen Access
    A geospatial model to determine patterns in river ice cover breakup and jamming behaviour
    (2014-08) Sagin, Jay
    In the past, both empirical and process-based attempts have been made to predict river ice behaviour, in particular ice cover breakup and ice jamming occurrences. These methods perform with varying and limited success and tend to be site specific. A method is required which can simply estimate the predisposition of river reaches to ice breakup and jamming events. This paper introduces a geospatial modelling approach which can fulfil that task and improve the predictive power of ice cover breakup and ice jamming behaviour. The geospatial model can determine the most vulnerable sections along the studied reaches to such behaviour, which are phenomena entailing hydraulic, ice morphology and fluvial geomorphology. A geospatial model clusters hydraulic characteristics (e.g. discharge or stage), ice characteristics (e.g. ice thickness and ice type) and river geomorphological characteristics (e.g. sinuosity, slope, width, etc.) into common river features called Geomorphic Response Units (GRU). A statistical clustering technique such as principle component analysis (PCA) is used to derive these GRUs. It is assumed that certain GRUs will be more susceptible to certain ice cover behaviour, such as breakup and jamming of river ice. Data acquired along the Slave River and its delta in Canada is used to test the geospatial model. The main data sources are space-borne remote sensing MODIS imagery and traditional and local knowledge from members of the communities alongside the river, in particular Fort Resolution and Fort Smith
  • ItemOpen Access
    Groundwater inflow modeling for a Kazakhstan copper ore deposit
    (2015) Sagin, Jay; Yerikuly, Zhaiyk; Zhaparkhanov, Slyamhan; Panichkin, Vladimir; Miroshnichenko, Oxana; Mashtayeva, Shamshagul
    Mining exploration is widely spread throughout Kazakhstan and it is an important part of the country’s economy. However, mining can create landslides, as well as both surface and groundwater pollution. The purpose of this research is to model the water movement and water volume changes for one of Kazakhstan's mining operations. In this study, we have modeled and predicted the water volume changes within a mining operation for the next 50 years, until the year 2065. The sulphide-ore mining operation, which was studied, is located in East Kazakhstan. Several mining development scenarios with groundwater volume changes were prepared. One of the modeling scenarios was related to the mining pit exploration up to a depth of 100 meters. The groundwater inflow was computed at 106.3 m3/hour, or 2551.6 m3/day for this scenario. Another modeling scenario for the same mining pit had a depth at 585 meters. The groundwater inflow for this scenario was computed at 268.6 m3/hour, or 6447.3 m3/day. Calibration and verification were provided for the modeling work, and results were compared to the water balance. The results of this work could be considered for the engineering design to drain the groundwater from the mining pit. This research work and methodology are replicable and could be applied to other mining explorations and groundwater inflow prediction analyses. The methodology can be adapted to open pit mines under similar conditions
  • ItemOpen Access
    Development of new type of wound dressing based on cryogel matrix with incorporated nanoparticles
    (The 15th IUMRS-International Conference in Asia (IUMRS-ICA 2014), 2014-08) Saliev, Timur; Kulsharova, Gulsim; Akhmetova, Alma; Nurgozhin, Talgat; Whitby, Ray D.L.
    A cryogel (polymethyl methacrylate) has been chosen as a basis for new type of wound dressings, where incorporated silver and gold nanoparticles do provide effective antibacterial protection [1]. This function will be enhanced by extracorporeal application of microwave radiation in safe regime.
  • ItemOpen Access
    Economical comparison among rechargeable batteries for integrating renewable energy into electrical grids
    (IMIE 2015, 2015-06) Hara, Toru; Moldabayeva, Azhar; Korzhynbayeva, Kuralay; Melisova, Malika; Kurmanbayeva, Indira; Bakenov, Zhumabay
    In this paper, economical comparison is conducted among non-toxic, non-flammable rechargeable batteries for integrating renewable energy into electrical grids. Two types of recently developed non-toxic aqueous batteries, "flow assisted Zn/NiOOH battery" and "half capacitor - half battery" (AC/NiOOH and AC/NaMnO2, AC denotes activated carbon. The AC electrode can be considered "a half capacitor", and the NiOOH or NaMnO2 electrode can be considered "a half battery"), are introduced and analyzed. These newly developed energy storage devices offer less expensive solutions for large scale energy storage than conventional batteries such as lithium-ion batteries, lead-acid batteries, vanadium redox flow batteries, and nickel metal hydride batteries. A newly started aqueous battery development, flow -assist-free Zn/NiOOH battery is also presented.